Mechanical face seals

Abstract

A mechanical face seal for providing a seal between a shaft and a housing includes a first seal face member mounted on the shaft in fixed rotational and axial relationship and sealed with respect thereto and a second seal face member mounted in fixed rotational relationship but moveable axially of the housing; said second seal face member being sealed with respect to the housing by means of a sealing element, the sealing element being located in a groove defined between opposed surfaces of the second seal face member and housing, the wall of the groove between the sealing element and the side of the seal exposed to a product being defined by a low friction insert slidably mounted on the second seal face member and providing a close clearance with the housing.

I claim: 
     
       1. A mechanical face seal for providing a seal between a pair of relatively rotatable components comprising a first seal face member mounted in fixed axial and rotational relationship and sealed with respect to one component and a second seal face member mounted in fixed rotational relationship but moveable axially of the other component, said first and second seal face members being axially aligned so that opposed faces may be urged into sealing engagement, said second seal face member being sealed with respect to said other component by means of a sealing element located in a circumferential groove defined between opposed surfaces of the second seal face member and said other component, the wall of the groove between the sealing element and the side of the seal exposed to a product being defined at least in part by a low friction insert slidingly mounted on one of the opposed surfaces of the seal face member and said other component and a close clearance with the other opposed surface. 
     
     
       2. A mechanical face seal according to claim 1 in which the insert is of L-section, the insert being slidably located on a stepped portion of the second seal face member, the flange of the insert defining one wall of the groove between the opposed surfaces of the second seal face member and said other component. 
     
     
       3. A mechanical face seal according to claim 1 in which the insert is formed from a plurality of rings, slidably located one inside another. 
     
     
       4. A mechanical face seal according to claim 1 in which the insert is made of PTFE. 
     
     
       5. A mechanical face seal according to claim 1 in which the insert defines a radial face which is exposed to fluid under pressure for pressure balancing purposes.